The invention relates to an apparatus for providing single adjustment dual-null pressure setting of nozzle pressures in a pilot stage.
Existing nozzle-flapper and other types of hydraulic valves require individual precision settings of each nozzle during assembly of the hydraulic device. During the assembly process, each part is precisely positioned. This need for precision is due to the typically small spacing between a nozzle and flapper. For example, the spacing may be between 0.002 and 0.004 inches. The spacing is important in the hydraulic valves as the spacing must be precise in order to balance pressures. Existing processes require either precision parts or precision assembly processes, or both. Despite the use of precision parts and precision assembly which are both costly and time consuming, the setting may not be precise in the differential pressure nozzles and a null offset will result. These differences or null offsets are undesirable, as they hinder the ability of the hydraulic valve to properly operate with differential pressures.
This problem of null offsets makes manufacturing of nozzle flapper hydraulic valves time consuming and costly.
It is therefore a primary objective of the present invention to provide an adjustable pressure setting for a pressure control pilot valve.
It is a further objective of the present invention to provide a pressure setting that permits multiple pressure levels to be adjusted with a single adjustment in such a valve.
It is a further objective of the present invention to improve the manufacturing process of nozzle-flapper hydraulic valves.
It is a still further objective of the present invention to provide a null adjustment that reduces manufacturing cost and/or time for nozzle-flapper hydraulic valves.
These and other objectives of the present invention will become apparent from this specification and claims.
The invention is a single adjustment dual-null pressure setting for hydraulic valves. The invention provides for an adjustment at the pivot of a flapper allowing multiple nozzles in the same plane to be adjusted through a single adjustment in order to reduce differential null pressures.
The invention makes a single adjustment at the location of the pivot of a flapper. The adjustment may be made by a pin such as a finely threaded screw or a press fit shaft. The null adjustment pin contacts a pivot pin. By adjusting the null adjustment pin, the location of the pivot pin is adjusted. The adjustment of the pivot pin causes the position of the flapper relative to each nozzle to change. In this manner, the adjustment can be made until a point is reached where each individual null pressure is established without a differential pressure.